This application claims priority based on a continuation of Ser. No. 09/667,151 filed Sep. 21, 2000 U.S. Pat. No. 6,668,935, issued Dec. 30, 2003, which was based on Provisional Application No. 60/155,866, filed in the United States on Sep. 24, 1999.
1. Field of the Invention
The present invention relates to the field of flow control. More specifically, the invention relates to a device and method for controlling the flow of fluids in a wellbore that, in one embodiment, provides for full tubing flow.
2. Background of the Related Art
The economic climate of the petroleum industry demands that oil companies continually improve their recovery systems to produce oil and gas more efficiently and economically from sources that are becoming increasingly difficult to exploit without increasing the cost to the consumer. One successful technique currently employed is the drilling of deviated wells, in which a number of horizontal wells are drilled from a central vertical borehole. In such wells, and in standard vertical wells, the well may pass through various hydrocarbon bearing zones or may extend through a single zone for a long distance. One method to increase the production of the well is to perforate the well in a number of different locations, either in the same hydrocarbon bearing zone or in different hydrocarbon bearing zones, and thereby increase the flow of hydrocarbons into the well.
One problem associated with producing from a well in this manner relates to the control of the flow of fluids from the well and to the management of the reservoir. For example, in a well producing from a number of separate zones (or from laterals in a multilateral well) in which one zone has a higher pressure than another zone, the higher pressure zone may produce into the lower pressure zone rather than to the surface. Similarly, in a horizontal well that extends through a single zone, perforations near the “heel” of the well, i.e., nearer the surface, may begin to produce water before those perforations near the “toe” of the well. The production of water near the heel reduces the overall production from the well. Likewise, gas coning may reduce the overall production from the well.
A manner of alleviating this problem is to insert a production tubing into the well, isolate each of the perforations or laterals with packers, and control the flow of fluids into or through the tubing. However, typical flow control systems provide for either on or off flow control with no provision for throttling of the flow. To fully control the reservoir and flow as needed to alleviate the above described problem, the flow is throttled. A number of devices have been developed or suggested to provide this throttling although each has certain drawbacks. Note that throttling may also be desired in wells having a single perforated production zone.
Specifically, the prior devices are typically either wireline retrievable valves, such as those that are set within the side pocket of a mandrel, or tubing retrievable valves that are affixed to the tubing string. The wireline retrievable valve has the advantage of retrieval and repair while providing effective flow control into the tubing without restricting the production bore. However, one drawback associated with the current wireline retrievable-type valves is that the valves cannot attain “full bore flow.” An important consideration in developing a flow control system pertains to the size of the restriction created into the tubing. It is desirable to have full bore flow, meaning that the flow area through the valve when fully open should be at least as large as the flow area of the tubing so that the full capacity of the tubing may be used for production. Therefore, a system that provides full bore flow through the valve is desired.
One area of particular concern relating to downhole valves is the erosion caused by the combination of high flow rates, differential pressure and the properties of the fluids, which may contain solids, such as sand. Erosion of the tools results in premature failure of the valves.
A need remains for a flow control system that provides for full bore flow and for an efficient, reliable, erosion-resistant system that can withstand the caustic environment of a wellbore, including a deviated wellbore.